A wide variety of coatings have been used to coat the surfaces of food and beverage containers. For example, metal cans are sometimes coated using coil coating or sheet coating operations; that is, a plane or coil or sheet of a suitable substrate, for example, steel or aluminum, is roll coated or electrodeposited with a suitable composition and cured. The coated substrate is then formed into the can body or can end. Alternatively, the coating composition may be applied, for example, by spraying, dipping and electrodeposition, to the formed can and then cured. Coatings for food and beverage containers are typically capable of high speed application to the substrate and provide the necessary properties when cured to perform in a demanding end use. For example, the coating should be safe for food contact and have acceptable adhesion to the substrate.
Many of the coating compositions for food and beverage containers are based on epoxy resins that are the polyglycidyl ethers of bisphenol A. Use of bisphenol A and derivatives thereof, such as diglycidyl ethers of bisphenol A (BADGE), epoxy novolak resins and polyols prepared with bisphenol A and bisphenol F have recently come under attack. Although the balance of scientific evidence available to date indicates that small trace amounts of BPA or BADGE that might be released from existing coatings does not pose health risks to humans, these compounds are nevertheless perceived by some as being harmful to human health. Consequently, there is a strong desire to eliminate these compounds from coatings for food and beverage containers. Accordingly, packaging coating compositions for food and/or beverage packaging that do not contain extractable quantities of BPA and/or derivatives thereof while providing suitable properties are therefore desired.